Sandbox using Docker

This repository contains images for running codes in different languages against certain testcases to effectively sandbox the execution.

Initial Setup

• Install the latest stable version of Docker.
• Set the path to the code to be executed in an environment variable

  export PATH_TO_CODE="<path_to_code>"
  

• Save each testcase in a separate file, all of which are present in one directory. Make sure that only the testcases for this code are present in that directory.
• Set the path to this directory containing all testcases in an environment variable

  export PATH_TO_TESTCASES="<path_to_testcases_directory>"
  

Build and run the containers

There are separate configurations for each supported language in the docker directory. The instructions present in the respective README can be followed to build and run the containers.

Building images for other languages

To support other languages follow these steps:

1. Create a Dockerfile. Replace <image> with iron/LANGUAGE:dev.
   (Example - iron/gcc:dev or iron/java:1.8-dev)

   FROM <image>
   
   RUN apk add --no-cache bash
   
   WORKDIR /sandbox
   COPY docker-entrypoint.sh .
   ENTRYPOINT ["bash", "docker-entrypoint.sh"]
   

   Refer iron-io for more details.

2. Now, create a docker-entrypoint.sh with the following content.
   (Replace <extension> with the appropriate extension for the language.)

   #!/bin/bash
   
   submission_directory="/sandbox/submission"
   testcases_directory="/sandbox/testcases"
   mkdir -p $submission_directory/output $submission_directory/error
   
   cd $submission_directory
   mv code code.<extension>

3. Once this is done write further code to compile the program code.<extension> and redirect output as follows:
   (Redirection here handles compilation output.)

   <Bash command for compiling "code.<extension>"> 2>"$submission_directory/compilation_error.err"
   if [[ $? -ne 0 ]]; then
       exit 145 # Compilation error. Terminate.
   fi

4. Once compiled run the program and redirect the output as follows:
   (Redirection here handles output and runtime errors if any.)

   for testcase in $(ls $testcases_directory); do
       <code to run the program> 0<"$testcases_directory/$testcase" \
           1>"$submission_directory/output/$testcase" \
           2>"$submission_directory/error/$testcase"
   done

5. Final file structure should look like this.

   • /sandbox
     
     • /docker
       
       • /<language>
         
         • /docker-entrypoint.sh
           
         • /Dockerfile
           
         • /README.md (Optional)
           

6. Now to build a image with this docker file run the command from sandbox folder.
   

   docker build -t cpjudge/<language> ./docker/<language>`

   Note: Here, we explicitly name the image built as cpjudge/<language>.
   This is essential because sandbox.go (Sandbox service) expects the image to be named in this format.

References

• Time Limit Constraints per language